soundproof room
A room designed to block external noise or prevent sound from escaping, used in recording studios, practice rooms, and industrial settings.
He built a soundproof room at home and practices piano until late at night.
The soundproof room in this studio completely blocks outside noise.
Compound of 防音 (ぼうおん, 'soundproofing') and 室 (しつ, 'room').